updated plain text techniques

I've updated the plain text techniques, based on the comments in the
survey and on the decision from the teleconference.

http://trace.wisc.edu/wcag_wiki/index.php?title=Using_standard_text_form
atting_conventions_for_paragraphs
http://trace.wisc.edu/wcag_wiki/index.php?title=Using_standard_text_form
atting_conventions_for_lists
http://trace.wisc.edu/wcag_wiki/index.php?title=Using_standard_text_form
atting_conventions_for_headings

Loretta Guarino Reid
lguarino@adobe.com
Adobe Systems, Acrobat Engineering